Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already cover the safety profile (readOnly, non-destructive), and the description adds genuine value beyond them: it clarifies the return mirrors the label page, flags the Email Recipients line, and explicitly states it sends nothing to the customer. It also discloses the API-key/access prerequisite.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Three short sentences, front-loaded with what the tool returns before the secondary clarifications. Efficient, with no sentence that could be cleanly dropped, though the 'sends nothing' line is slight padding on top of the readOnly annotation.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a single-record get with one fully documented parameter and no output schema, the description supplies enough: it sketches the returned fields, notes the tracking-email indicator, and states the auth requirement. Nothing an agent needs to call it correctly is missing.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100% and the single shipment_id parameter is fully documented in the schema, including its source (list_shipments, buy_label, buy_batch). The description adds no parameter-level detail, so the schema does the heavy lifting and baseline 3 applies.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb (get) and resource (a single shipment), and enumerates the fields returned (service, cost, insurance, tracking number, status). The 'One shipment' phrasing implicitly separates it from list_shipments, though it never names that sibling.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

Usage is implied by 'One shipment' – retrieve a single record's details – but there is no explicit when-to-use versus list_shipments or any other Pirate Ship sibling, nor any exclusion. Context exists but is left to inference.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.